Sulfonamide compound, polymer compound, resist material and pattern formation method

ABSTRACT

A base polymer of a resist material includes a unit represented by a general formula of the following Chemical Formula 3: 
     
       
         
         
             
             
         
       
         
         
           
             wherein R 1 , R 2  and R 3  are the same or different and are a hydrogen atom, a fluorine atom, a straight-chain alkyl group, a branched or cyclic alkyl group or a fluoridated alkyl group with a carbon number not less than 1 and not more than 20; R 4  is a straight-chain alkylene group or a branched or cyclic alkylene group with a carbon number not less than 0 and not more than 20; and R 5  and R 6  are the same or different and are a hydrogen atom, a straight-chain alkyl group, a branched or cyclic alkyl group, a fluoridated alkyl group with a carbon number not less than 1 and not more than 20, or a protecting group released by an acid.

RELATED APPLICATION

This application is a divisional of application Ser. No. 10/932,316,filed Sep. 2, 2004 now U.S. Pat. No. 7,166,418, which claims priority toJapanese Patent Applications 2003-311374, filed on Sep. 3, 2003, whichare all incorporated herein by reference.

This application claims the benefit of Japanese Patent Application No.2003-311374 filed on Sep. 3, 2003, the disclosure of which is hereinincorporated by reference in its entirety.

BACKGROUND OF THE INVENTION

The present invention relates to a resist material or a chemicallyamplified resist material suitably used in refinement technique, apolymer compound useful as a base polymer of the resist material, asulfonamide compound used as a material monomer of the polymer compound,and a pattern formation method using the resist material.

In accordance with recent increase of the degree of integration and theoperation speed of an LSI, there are increasing demands for refinementof an interconnect pattern rule.

The refinement of the interconnect pattern rule has been rapidlydeveloped because of increased NA of a projection lens, improvedperformance of a resist material, a reduced wavelength of exposing lightand the like.

With respect to increase of resolution and sensitivity of a resistmaterial, a positive chemically amplified resist material using, as acatalyst, an acid generated through irradiation with exposing lightexhibits high performance and hence has become a leading resist materialparticularly in the field of deep UV lithography (see Japanese PatentPublication No. 2-27660 and Japanese Laid-Open Patent Publication No.63-27829).

Also, reduction of the wavelength of the exposing light from i line (ofa wavelength of a 365 nm band) to KrF excimer laser (of a wavelength of248 nm band) has brought a large technical innovation, and a resistmaterial for the KrF excimer laser was applied to 0.30 μm process atfirst and to a 0.18 μm rule in the course of time and is now applied tomass-production employing a 0.15 μm rule.

Furthermore, a 0.13 μm rule has already been studied. Thus, the speedfor development in the refinement has been increasing, and hence, it isnecessary to further improve transparency and substrate adhesiveness ofa resist material.

It is expected that the design rule can be further refined to 90 nm orless by using ArF excimer laser (of a wavelength of a 193 nm band) asthe exposing light. However, a conventionally used resin such as aNoborac resin and a poly(vinylphenol)-based resin has strong absorptionin the vicinity of the wavelength of the 193 nm band, and hence cannotbe used as a base polymer of a resist material to be employed in thiscase.

Therefore, for attaining transparency and dry etching resistance, use ofan acrylic resin or a cycloolefin-based alicyclic resin as a basepolymer has been examined (see Japanese Laid-Open Patent PublicationNos. 9-73173, 10-10739 and 9-230595 and WO97/33198).

The other references related to the background of the invention areJapanese Laid-Open Patent Publication Nos. 2000-330289 and 2002-250215;Tsuyohiko FUJIGAYA, Shinji ANDO, Yuji SHIBASAKI, Mitsuru UEDA, ShinjiKISHIMURA, Masayuki ENDO and Masaru SASAGO, “New Photoresist Materialfor 157 nm Lithography-2”, J. Photopolym. Sci. Technol., 15(4), 643-654(2002); T. Fujigaya, Y Shibasaki, S. Ando, S. Kishimua, M. Endo, M.Sasago and M. Ueda, Chem. Mater. 2003, 15, 1512; T. Fujigaya, Y.Shibasaki, S. Ando, S. Kishimura, M. Endo, M. Sasago, and M. Ueda, “ANew Photoresist Materials for 157 nm Lithography-2”, J. Photopolym. Sci.& Technol., 15, 643-654 (2002); and H. Iimori, S. Ando, Y Shibasaki, M.Ueda, S. Kishimura, M. Endo and M. Sasago, J. Photopolym. Sci. Technol.2003, 16, 601.

An acrylic resin has, however, a problem that a resultant resist patternis in a poor shape when it is used as a base polymer because it swellsin development, and an alicyclic resist has a problem that solubility ina developer and substrate adhesiveness are degraded when it is used as abase polymer because it has a strong hydrophobic property.

On the other hand, F₂ laser (of a wavelength of a 157 nm band) isexpected to attain refinement of the design rule to approximately 65 nmor less, but it is difficult to attain sufficient transparency of a basepolymer. It has been found that an acrylic resin that is used as a basepolymer in using ArF excimer laser does not transmit light at all, andthat a cycloolefin-based resin having a carbonyl bond has strongabsorption against the F₂ laser. Furthermore, poly(vinylphenol), whichis used as a base polymer in using KrF excimer laser, has an absorptionwindow (namely, a region that has high transparency because exposinglight is not absorbed therein) in the vicinity of a wavelength of a 160nm band, and hence the transmittance is slightly improved when it isused, but it has been found that the transmittance is still far frompractical level (that is, transmittance of 40% or more).

SUMMARY OF THE INVENTION

In consideration of the aforementioned conventional problems, an objectof the invention is providing a resist material and more specifically achemically amplified resist material that has high transmittance againstexposing light of a wavelength not longer than a 300 mm band, and inparticular, deep UV such as KrF laser (of a wavelength of a 248 nm band)or ArF laser (of a wavelength of a 193 nm band) or vacuum UV such as F₂laser (of a wavelength of a 157 nm band), Kr₂ laser (of a wavelength ofa 146 nm band), KrAr laser (of a wavelength of a 134 nm band) or Ar₂laser (of a wavelength of a 126 mm band), is good at substrateadhesiveness, does not swell in development and exhibits high solubilityin a developer; a novel polymer compound useful as a base polymer of theresist material; a sulfonamide compound used as a material monomer ofthe polymer compound; and a pattern formation method using the resistmaterial.

In this manner, since a carbonyl group or a double bond of carbon hasabsorption in the vicinity of the 157 nm band, it seems to be oneeffective method for improving the transmittance to reduce such a unit.

Furthermore, it has been found through recent study that transparency isremarkably improved in the vicinity of the 157 nm band by introducing afluorine atom into a base polymer. Actually, a polymer in which fluorineis introduced into an aromatic ring of poly(vinylphenol) attainstransmittance at almost practical level.

It has been found, however, that such a base polymer is difficult topractically use in a resist material because a negative reaction islargely proceeded through irradiation with high energy beams such as F₂laser.

Also, it has been found that an acrylic polymer or a polymer in whichfluorine is introduced into a polymer compound having, on a main chain,an aliphatic cyclic compound obtained from a norbornene derivative hashigh transparency and is free from the negative reaction. However, ithas been also found that the substrate adhesiveness of a resist film andpermeability of a developer tend to be degraded when the introducingrate of fluorine is increased for further improving the transparency.

The present inventors have earnestly made examination for achieving theobject, and as a result, have found that a resist material and moreparticularly a chemically amplified resist material that is good attransparency, has high substrate adhesiveness, does not swell indevelopment and exhibits high solubility in a developer can be obtainedwhen a polymer including a sulfonamide compound having a sulfonamidegroup on the side chain is used as a base polymer.

Specifically, a sulfonamide compound having a sulfonamide group on theside chain has high transmittance against exposing light of a wavelengthnot longer than a 300 nm band although it includes two sulfur-oxygendouble bonds. In addition, a resist film containing, as a base polymer,a polymer compound including a unit of a sulfonamide compound having asulfonamide group on the side chain is remarkably improved in thesubstrate adhesiveness and the developer permeability as compared with aresist film containing a base polymer of a simple fluorine-containingpolymer.

First, the mechanism of improving transparency and an effect attained bythe improvement of the transparency will be described.

It has been found that although a base polymer including a unit having asulfonamide group on the side chain has two sulfur-oxygen double bonds,it has high transmittance against exposing light of a wavelength notlonger than a 300 nm band. The unit having a sulfonamide group on theside chain can constitute a base polymer without using any carbonylgroup on all the side chains included in the base polymer. Therefore,since the base polymer can be obtained while suppressing the proportionof carbonyl groups having a high absorption property against exposinglight of a wavelength of a 200 nm band in particular, the transparencyof the resist film against light of a shorter wavelength band can beimproved.

Accordingly, since the exposing light reaches the bottom of the resistfilm in pattern exposure, the resist film is changed to a developablestate even in a bottom portion thereof, or a sufficient amount of acidis generated in an exposed portion and hence the resist film is changedto a developable state even in the bottom portion thereof. As a result,a good resist pattern can be formed.

It is noted that when a plurality of CF₃ groups are introduced into thebase polymer, the transparency of the resist film against the exposinglight is improved. This is for the following reason: When a plurality ofF atoms are present in the base polymer, the absorption peak of theexposing light against a resist film having a structure in whichsubstituent groups in any positions are not replaced with F atoms isshifted, resulting in moving the initial absorption band of the exposinglight.

Furthermore, a resist film including a fluorine-containing polymer as abase polymer is generally of a type having carbonyl ester on the sidechain. On the other hand, the base polymer according to the presentinvention has a sulfonamide group on the side chain. In a sulfonamidegroup, an oxygen atom with a strong negative property and large polarityand a sulfur atom are bonded through a double bond, and free electronson the oxygen atom not related to the bond are present in a delocalizedstate. Therefore, when a sulfonamide group is introduced into the sidechain of the base polymer, a portion of the base polymer correspondingto the sulfonamide group exhibits strong polarity, and hence, electronicinteraction is easily caused between the sulfonamide group and asubstrate or ion interaction is caused between the sulfonamide group andan alkaline group included in a developer. As a result, the substrateadhesiveness of the resist film is improved and reactivity of an exposedportion against the developer is improved.

Moreover, it has been found that swelling of the resist film can besuppressed when the base polymer has a sulfonamide group on the sidechain.

A conventional acrylic resist material includes, on the side chain, aunit that is changed into a carboxylic acid group through exposure as aunit for causing a reaction with the developer. In a carboxylic acidgroup, a H atom and an O atom interacts with each other through ahydrogen bond as shown in Chemical Formula 6 below, and hence, thecarboxylic acid group tends to form a hexagonal structure in which twomolecules oppose each other. Since electrons form an octet in thishexagonal structure, the structure is sterically stable. When bondshaving such a structure are generated in various portions of the basepolymer after the exposure, three-dimensional bonds tend to be formedbetween the side chains of the polymer, and hence the polymer is easilyformed in a mesh structure. As a result, the resist film swells.

On the other hand, the resist material of the present invention includesa unit having a sulfonamide group on the side chain as the unit forcausing a reaction with the developer after the exposure. In asulfonamide group, bonds mutually easily coupled cannot be formed owingto its structure differently from a carboxylic acid group. Therefore,even when the unit that can react with a developer is formed after theexposure, the terminal groups of the base polymer minimally formthree-dimensional bonds, and a mesh structure is minimally formed. As aresult, swelling of the resist film can be suppressed.

The present invention was devised on the basis of the aforementionedfindings, and is specifically practiced as follows:

The sulfonamide compound of this invention is represented by a generalformula of the following Chemical Formula 7:

wherein R¹, R² and R³ are the same or different and are a hydrogen atom,a fluorine atom, a straight-chain alkyl group, a branched or cyclicalkyl group, or a fluoridated alkyl group with a carbon number not lessthan 1 and not more than 20; R⁴ is a straight-chain alkylene group or abranched or cyclic alkylene group with a carbon number not less than 0and not more than 20; and R⁵ and R⁶ are the same or different and are ahydrogen atom, a straight-chain alkyl group, a branched or cyclic alkylgroup, or a fluoridated alkyl group with a carbon number not less than 1and not more than 20, or a protecting group released by an acid.

The sulfonamide compound of this invention has a sulfonamide group (aSO₂N group) on the side chain, and hence, a sulfur atom (S) included inthe sulfonamide group has positive polarity while an oxygen atom (O)included in the sulfonamide group has negative polarity. Therefore, thecompound having the sulfonamide group has a high hydrophilic property.Also, since the sulfonamide compound has the sulfonamide group on theside chain, the transparency thereof is also improved.

In the sulfonamide compound of the invention, the protecting groupreleased by an acid is preferably an acetal group.

Thus, since an acetal group includes an ether bond and has an unpairedelectron pair on an oxygen atom, it has high reactivity against an acid.In other words, it needs smaller activation energy for reacting with anacid. Therefore, the protecting group of the acetal group can be easilyreleased by an acid. Also, the sulfonamide compound having the acetalprotecting group is obtained by, for example, allowing a sulfonamidecompound to react with a vinyl ether compound or methyl ether halide.

In the sulfonamide compound of this invention, the acetal group ispreferably an alkoxyethyl group or an alkoxymethyl group.

Furthermore, examples of the alkoxyethyl group are an adamantyloxyethylgroup, a t-butyloxyethyl group, an ethoxyethyl group and a methoxyethylgroup. An adamantyloxyethyl group is obtained by, for example, allowinga sulfonamide compound to react with vinyl adamantane ether.

Also, examples of the alkoxymethyl group are an adamantyloxymethylgroup, a t-butyloxymethyl group, an ethoxymethyl group and amethoxymethyl group. An adamantyloxymethyl group is obtained by, forexample, allowing a sulfonamide compound with chloromethyl adamantaneether.

The polymer compound of this invention includes a unit represented by ageneral formula of the following Chemical Formula 8 and has aweight-average molecular weight of 1,000 or more and 500,000 or less:

wherein R¹, R² and R³ are the same or different and are a hydrogen atom,a fluorine atom, a straight-chain alkyl group, a branched or cyclicalkyl group, or a fluoridated alkyl group with a carbon number not lessthan 1 and not more than 20; R⁴ is a straight-chain alkylene group or abranched or cyclic alkylene group with a carbon number not less than 0and not more than 20; and R⁵ and R⁶ are the same or different and are ahydrogen atom, a straight-chain alkyl group, a branched or cyclic alkylgroup, or a fluoridated alkyl group with a carbon number not less than 1and not more than 20, or a protecting group released by an acid.

The polymer compound of this invention has a sulfonamide group on theside chain of the unit, and hence, a sulfur atom included in thesulfonamide group has positive polarity while an oxygen atom included inthe sulfonamide group has negative polarity. Therefore, the unit havingthe sulfonamide group has a high hydrophilic property. Also, since thepolymer compound has the sulfonamide group on the side chain of theunit, the transparency thereof is also improved.

The resist material of this invention includes a base polymer containinga polymer compound including a unit represented by a general formula ofthe following Chemical Formula 9:

wherein R¹, R² and R³ are the same or different and are a hydrogen atom,a fluorine atom, a straight-chain alkyl group, a branched or cyclicalkyl group or a fluoridated alkyl group with a carbon number not lessthan 1 and not more than 20; R⁴ is a straight-chain alkylene group or abranched or cyclic alkylene group with a carbon number not less than 0and not more than 20; and R⁵ and R⁶ are the same or different and are ahydrogen atom, a straight-chain alkyl group, a branched or cyclic alkylgroup or a fluoridated alkyl group with a carbon number not less than 1and not more than 20, or a protecting group released by an acid.

The resist material of this invention includes the base polymer having asulfonamide group on the side chain of the unit, and hence, a sulfuratom included in the sulfonamide group has positive polarity while anoxygen atom included in the sulfonamide group has negative polarity.Therefore, the unit having the sulfonamide group has a high hydrophilicproperty. Accordingly, the substrate adhesiveness of a resultant resistfilm is improved and the resist film is free from swelling and is goodat developer solubility, and hence, a resist pattern can be formed in agood shape. Also, since the base polymer has the sulfonamide group onthe side chain of the unit, although it includes two sulfur-oxygendouble bonds, it has high transmittance against exposing light of awavelength not longer than a 300 nm band.

In the resist material of this invention, the protecting group releasedby an acid is preferably an acetal group.

Thus, since an acetal group includes an ether bond and has an unpairedelectron pair on an oxygen atom, it has high reactivity against an acid.In other words, it needs smaller activation energy for reacting with anacid. Therefore, the protecting group of the acetal group can be easilyreleased by an acid.

In the resist material of this invention, the acetal group is preferablyan alkoxyethyl group or an alkoxymethyl group.

Examples of the alkoxyethyl group are an adamantyloxyethyl group, at-butyloxyethyl group, an ethoxyethyl group and a methoxyethyl group.

Examples of the alkoxymethyl group are an adamantyloxymethyl group, at-butyloxymethyl group, an ethoxymethyl group and a methoxymethyl group.

The resist material of this invention preferably further includes anacid generator for generating an acid through irradiation with light.

Thus, a positive chemically amplified resist material capable ofexhibiting the aforementioned effects can be realized.

The resist material of this invention preferably further includes adissolution inhibitor for inhibiting dissolution of the base polymer.

Thus, the dissolution contrast of the resultant resist film is improved.

The first pattern formation method of this invention includes the stepsof forming a resist film made of a resist material containing a basepolymer including a polymer compound having a unit represented by ageneral formula of the following Chemical Formula 10; performing patternexposure by selectively irradiating the resist film with exposing lightof high energy beams of a wavelength not shorter than a 100 nm band andnot longer than a 300 nm band or not shorter than a 1 nm band and notlonger than a 30 nm band or electron beams; and forming a resist patternby developing the resist film after the pattern exposure:

wherein R¹, R² and R³ are the same or different and are a hydrogen atom,a fluorine atom, a straight-chain alkyl group, a branched or cyclicalkyl group or a fluoridated alkyl group with a carbon number not lessthan 1 and not more than 20; R⁴ is a straight-chain alkylene group or abranched or cyclic alkylene group with a carbon number not less than 0and not more than 20; and R⁵ and R⁶ are the same or different and are ahydrogen atom, a straight-chain alkyl group, a branched or cyclic alkylgroup or a fluoridated alkyl group with a carbon number not less than 1and not more than 20, or a protecting group released by an acid.

In the first pattern formation method of this invention, the basepolymer has a sulfonamide group on the side chain of the unit, andhence, a sulfur atom included in the sulfonamide group has positivepolarity while an oxygen atom included in the sulfonamide group hasnegative polarity. Therefore, the unit having the sulfonamide group hasa high hydrophilic property. Accordingly, the substrate adhesiveness ofthe resist film is improved and the resist film is free from swellingand is good at developer solubility, and hence, the resist pattern canbe formed in a good shape. Also, since the base polymer has thesulfonamide group on the side chain of the unit, although it includestwo sulfur-oxygen double bonds, it has high transmittance againstexposing light of a wavelength not longer than a 300 nm band.

The second pattern formation method of this invention includes the stepsof forming a resist film made of a resist material containing a basepolymer including a polymer compound having a unit represented by ageneral formula of the following Chemical Formula 11; supplying a liquidonto the resist film; performing pattern exposure, with the liquidprovided on the resist film, by selectively irradiating the resist filmwith exposing light of high energy beams of a wavelength not shorterthan a 100 nm band and not longer than a 300 nm band or not shorter thana 1 nm band and not longer than a 30 nm band or electron beams; andforming a resist pattern by developing the resist film after the patternexposure:

wherein R¹, R² and R³ are the same or different and are a hydrogen atom,a fluorine atom, a straight-chain alkyl group, a branched or cyclicalkyl group, or a fluoridated alkyl group with a carbon number not lessthan 1 and not more than 20; R⁴ is a straight-chain alkylene group or abranched or cyclic alkylene group with a carbon number not less than 0and not more than 20; and R⁵ and R⁶ are the same or different and are ahydrogen atom, a straight-chain alkyl group, a branched or cyclic alkylgroup or a fluoridated alkyl group with a carbon number not less than 1and not more than 20, or a protecting group released by an acid.

In the second pattern formation method of this invention, the step ofperforming the pattern exposure is carried out by employing immersionlithography, and hence, the resolution of the resist film is improved.In the immersion lithography, a region between a condensing lens and aresist film formed on a wafer in an exposure system is filled with aliquid having a refractive index higher than that of the air. Thus,theoretically, the NA (numerical aperture of a lens) of the exposuresystem can be increased to the refractive index of the liquid at itsbest, resulting in improving the dissolution of the resist film. Also,the focal depth can be increased by this method.

Specific effects obtained in this invention are as follows: Since thebase polymer of the resist material has a sulfonamide group on the sidechain in this invention, high resolution can be attained by employingthe immersion lithography in particular. In a sulfonamide group, anoxygen atom having a strong negative property and large polarity and asulfur atom are bonded through a double bond and a nitrogen atom thateasily attains a positive polarity is bonded to the sulfur atom.Therefore, free electrons on the oxygen atom not related to the bondwith the sulfur atom are present in a delocalized state. In other words,the sulfonamide group is a substituent group having high polarity, andtherefore, when the base polymer includes a vinyl sulfonamide unit as inthis invention, there are a plurality of sulfonamide groups on the sidechain. Accordingly, electronic interaction (chemical interaction) iscaused between an oxygen atom having a strong negative property of asulfonamide group bonded to a side chain of one base polymer and anitrogen atom having a strong positive property of a sulfonamide groupbonded to a side chain of another base polymer, resulting in causingstrong interaction between the base polymers included in the resistfilm.

Accordingly, even when the liquid is provided on the resist film in theexposure employing the immersion lithography, the strong interactioncaused within the resist film brings a force for mutually holdingsubstances included in the resist film. Therefore, a substance includedin the resist film is minimally eluted from the resist film into theliquid. Also, the substituent groups are already bonded to one anotherthrough the chemical interaction within the base polymer included in theresist film, interaction is minimally caused between constitutingmolecules of the liquid employed in the exposure by the immersionlithography and the base polymer. Therefore, the liquid can be preventedfrom invading the resist film. As a result, high resolution peculiar tothe exposure by the immersion lithography can be kept and the solubilityin a developer can be high, so that stable pattern formation can becarried out.

In the first or second pattern formation method of this invention, theprotecting group released by an acid is preferably an acetal group.

Thus, since an acetal group includes an ether bond and has an unpairedelectron pair on an oxygen atom, it has high reactivity against an acid.In other words, it needs smaller activation energy for reacting with anacid. Therefore, the protecting group of the acetal group can be easilyreleased by an acid.

In the first or second pattern formation method of this invention, theresist material preferably further includes an acid generator forgenerating an acid through irradiation with light.

Thus, the aforementioned effects can be realized through patternformation using a positive chemically amplified resist material.

In the first or second pattern formation method of this invention, theresist material preferably further includes a dissolution inhibitor forinhibiting dissolution of the base polymer.

Thus, the dissolution contrast of the resist film is improved.

In the first or second pattern formation method of this invention, theexposing light may be KrF laser, ArF laser, F₂ laser, Kr₂ laser, KrArlaser, Ar₂ laser or soft X-rays.

In the second pattern formation method of this invention, the liquid maybe water or perfluoropolyether.

In the first or second pattern formation method of this invention, theresist film preferably has transmittance of 40% or more against theexposing light.

In the first or second pattern formation method of this invention, thebase polymer preferably has a trifluoromethyl group on a side chainthereof.

In this manner, since the sulfonamide compound or the polymer compoundof this invention has a sulfonamide group on the side chain, thecompound has a high hydrophilic property. Therefore, the substrateadhesiveness of a resultant resist film is improved, and the resist filmis free from swelling and is good at developer solubility, and hence, aresist pattern can be formed in a good shape. Also, since the compoundhas the sulfonamide group on the side chain, the transparency againstexposing light of a wavelength not longer than a 300 nm band is alsoimproved. In addition, the present invention is effective in patternformation using the immersion lithography.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A, 1B, 1C and 1D are cross-sectional views for showing proceduresin a pattern formation method of Examples 1 through 3 for embodyingEmbodiment 5 of the invention;

FIG. 2 is a diagram for showing an exemplified experiment performed forevaluating the pattern formation method of Embodiment 5; and

FIGS. 3A, 3B, 3C and 3D are cross-sectional views for showing proceduresin a pattern formation method of Example 6 for embodying Embodiment 6 ofthe invention.

DETAILED DESCRIPTION OF THE INVENTION Embodiment 1

A sulfonamide compound and a polymer compound according to Embodiment 1of the invention will now be described.

The sulfonamide compound of Embodiment 1 is represented by a generalformula shown as Chemical Formula 12 below, and the polymer compound ofEmbodiment 1 includes a unit represented by a general formula shown asChemical Formula 13 below. The polymer compound of Embodiment 1 has aweight-average molecular weight of 1,000 through 500,000 and preferablyof 2,000 through 100,000.

In Chemical Formulas 12 and 13, R¹, R² and R³ are the same or differentand are a hydrogen atom, a fluorine atom, a straight-chain alkyl group,a branched or cyclic alkyl group or a fluoridated alkyl group with acarbon number not less than 1 and not more than 20; and R⁵ and R⁶ arethe same or different and are a hydrogen atom, a straight-chain alkylgroup, a branched or cyclic alkyl group or a fluoridated alkyl groupwith a carbon number not less than 1 and not more than 20, or aprotecting group released by an acid. It is noted that when the polymercompound of Embodiment 1 is used in a chemically amplified resistmaterial, at least one of R⁵ and R⁶ is a protecting group released by anacid.

Embodiment 2

A sulfonamide compound and a polymer compound according to Embodiment 2of the invention will now be described.

The sulfonamide compound of Embodiment 2 is represented by a generalformula shown as Chemical Formula 14 below, and the polymer compound ofEmbodiment 2 includes a unit represented by a general formula shown asChemical Formula 15 below. The polymer compound of Embodiment 2 has aweight-average molecular weight of 1,000 through 500,000 and preferablyof 2,000 through 100,000.

In Chemical Formulas 14 and 15, R¹, R² and R³ are the same or differentand are a hydrogen atom, a fluorine atom, a straight-chain alkyl group,a branched or cyclic alkyl group or a fluoridated alkyl group with acarbon number not less than 1 and not more than 20; R⁴ is astraight-chain alkylene group or a branched or cyclic alkylene groupwith a carbon number not less than 1 and not more than 20; and R⁵ and R⁶are the same or different and are a hydrogen atom, a straight-chainalkyl group, a branched or cyclic alkyl group or a fluoridated alkylgroup with a carbon number not less than 1 and not more than 20, or aprotecting group released by an acid. It is noted that when the polymercompound of Embodiment 2 is used in a chemically amplified resistmaterial, at least one of R⁵ and R⁶ is a protecting group released by anacid.

In the sulfonamide compound represented by the general formula ofChemical Formula 12 or 14 and in the polymer compound including the unitrepresented by the general formula of Chemical Formula 13 or 15 ofEmbodiment 1 or 2, specific examples of the straight-chain alkyl groupor the branched or cyclic alkyl group with a carbon number not less than1 and not more than 20 are a methyl group, an ethyl group, a propylgroup, an isopropyl group, a n-propyl group, a n-butyl group, asec-butyl group, a tert-butyl group, a cyclopentyl group, a cyclohexylgroup, a cyclohexymethyl group, a 2-ethylhexyl group, a n-octyl group, a2-adamantyl group and a (2-adamantyl)methyl group. In any of thesegroups, the carbon number is preferably not less than 1 and not morethan 12 and is more preferably not less than 1 and not more than 10.

Also, in the sulfonamide compound represented by the general formula ofChemical Formula 12 or 14, or in the polymer compound including the unitrepresented by the general formula of Chemical Formula 13 or 15, thefluoridated alkyl group may be any of the aforementioned alkyl groups inwhich fluorine atoms are substituted for part or whole of hydrogenatoms, and specific examples are a trifluoromethyl group, a2,2,2-trifluoroethyl group, a 3,3,3-trifluoropropyl group, a1,1,1,3,3,3-hexafluoroisopropyl group, a 1,1,2,2,3,3,3-heptafluoropropylgroup, and groups represented by respective general formulas shown inChemical Formula 16 below.

In Chemical Formula 16, R¹² is a hydrogen atom, a fluorine atom, astraight-chain alkyl group, a branched or cyclic alkyl group or afluoridated alkyl group with a carbon number not less than 1 and notmore than 20; and f is an integer not less than 0 and not more than 10.

Now, the protecting group released by an acid (that is, R⁵ and R⁶) usedin the sulfonamide compound represented by the general formula ofChemical Formula 12 or 14 or in the polymer compound including the unitrepresented by the general formula of Chemical Formula 13 or 15 will bedescribed. As the protecting group, any of various groups can be usedand in particular, a group represented by a general formula shown asChemical Formula 17, 18 or 19 below is preferably used.

The general formula shown as Chemical Formula 17 will now be described.

In Chemical Formula 17, R¹³ is a tertiary alkyl group with a carbonnumber not less than 4 and not more than 20 and preferably not less than4 and not more than 15, an oxoalkyl group with a carbon number not lessthan 4 and not more than 20, or a group represented by Chemical Formula19. Specific examples of the tertiary alkyl group are a tert-butylgroup, a tert-amyl group, a 1,1-diethylpropyl group, a1-ethylcyclopentyl group, a 1-butylcyclopentyl group, a1-ethylcyclohexyl group, a 1-butylcyclohexyl group, a1-ethyl-2-cyclopentenyl group, a 1-ethyl-2-cyclohexenyl group, a2-methyl-2-adamantyl group, etc. Specific examples of the oxoalkyl groupare a 3-oxocyclohexyl group, a 4-methyl-2-oxooxane-4-il group and a5-methyl-5-oxooxolane-4-il group. Also, g is an integer not less than 0and not more than 6.

Specific examples of the protecting group represented by ChemicalFormula 17 are a tert-butoxycarbonyl group, a tert-butoxycarbonylmethylgroup, a tert-amyloxycarbonyl group, a tert-amyloxycarbonylmethyl group,a 1,1-diethylpropyloxycarbonyl group, a1,1-diethylpropyloxycarbonylmethyl group, a1-ethylcyclopentyloxycarbonyl group, a1-ethylcyclopentyloxycarbonylmethyl group, a1-ethyl-2-cyclopentenyloxycarbonyl group, a1-ethyl-2-cyclopentenyloxycarbonylmethyl group, a1-ethoxyethoxycarbonylmethyl group, a2-tetrahydropyranyloxycarbonylmethyl group, a2-tetrahydrofuranyloxycarbonylmethyl group, etc.

Now, the general formula shown as Chemical Formula 18 will be described.

In Chemical Formula 18, R¹⁴ and R¹⁵ are the same or different and are ahydrogen atom, a straight-chain alkyl group with a carbon number notless than 1 and not more than 18 and preferably not less than 1 and notmore than 10, or a branched or cyclic alkyl group. Specific examples area methyl group, an ethyl group, a propyl group, an isopropyl group, an-butyl group, a sec-butyl group, a tert-butyl group, a cyclopentylgroup, a cyclohexyl group, a 2-ethylhexyl group and a n-octyl group.

Furthermore, in Chemical Formula 18, R¹⁶ is a univalent carbon hydride(which may include a hetero atom such as an oxygen atom) with a carbonnumber not less than 1 and not more than 18 and preferably not less than1 and not more than 10, and may be a straight-chain, branched or cyclicalkyl group, or such an alkyl group in which hydroxyl groups, alkoxygroups, oxo groups, amino groups or alkylamino groups are substitutedfor part of hydrogen atoms. Specific examples of R¹⁶ are substitutedalkyl groups shown in Chemical Formula 20 below.

In Chemical Formula 18, each of pairs of R¹⁴ and R¹⁵, R¹⁴ and R¹⁶, andR¹⁵ and R¹⁶ may be mutually bonded to form a ring. When they form aring, each of R¹⁴, R¹⁵ and R¹⁶ is a straight-chain or branched alkylenegroup with a carbon number not less than 1 and not more than 18 and morepreferably not less than 1 and not more than 10.

In the protecting group represented by Chemical Formula 18, specificexamples of the straight-chain or branched alkylene group are groupsshown in Chemical Formula 21 below:

Also, in the protecting group represented by Chemical Formula 18,specific examples of the cyclic alkylene group are atetrahydrofuran-2-il group, a 2-methyltetrahydrofuran-2-il group, atetrahydropyran-2-il group and a 2-methyltetrahydropyran-2-il group.

As the protecting group represented by Chemical Formula 18, anethoxyethyl group, a butoxyethyl group, an ethoxypropyl group, anadamantyloxyethyl group or an adamantyloxymethyl group is preferablyused.

Now, the general formula shown as Chemical Formula 19 will be described.

In Chemical Formula 19, each of R¹⁷, R¹⁸ and R¹⁹ is a univalent carbonhydride group such as a straight-chain alkyl group or a branched orcyclic alkyl group with a carbon number not less than 1 and not morethan 20, and may include a hetero atom such as oxygen, sulfur, nitrogenor fluorine.

In Chemical Formula 19, each of pairs of R¹⁷ and R¹⁸, R¹⁷ and R¹⁹, andR¹⁸ and R¹⁹ may be mutually bonded to form a ring together with a carbonatom bonded to these groups.

Specific examples of a tertiary alkyl group represented by ChemicalFormula 19 are a tert-butyl group, a triethylcarbyl group, a1-ethylnorbornyl group, a 1-methylcyclohexyl group, a 1-ethylcyclopentylgroup, a 2-(2-methyl)adamantyl group, a 2-(2-ethyl)adamantyl group, atert-amyl group, a 1,1,1,3,3,3-hexafluoro-2-methyl-isopropyl group, a1,1,1,3,3,3-hexafluoro-2-cyclohexyl-isopropyl group and groups shown inChemical Formula 22 below.

Chemical Formula 22, R²⁰ is a straight-chain, branched or cyclic alkylgroup bon number not less than 1 and not more than 6, and specificexamples are a methyl group, an ethyl group, a propyl group, anisopropyl group, a n-butyl group, a sec-butyl group, a n-pentyl group, an-hexyl group, a cyclopropyl group, a cyclopropylmethyl group, acyclobutyl group, a cyclopentyl group and a cyclohexyl group.

Also, in Chemical Formula 22, R²¹ is a straight-chain, branched orcyclic alkyl group with a carbon number not less than 2 and not morethan 6, and specific examples are an ethyl group, a propyl group, anisopropyl group, a n-butyl group, a sec-butyl group, a n-pentyl group, an-hexyl group, a cyclopropyl group, a cyclopropylmethyl group, acyclobutyl group, a cyclopentyl group and a cyclohexyl group.

Furthermore, in Chemical Formula 22, R²² and R²³ are the same ordifferent and are a hydrogen atom or a univalent carbon hydride group(which may include a hetero atom or may be bonded through a hetero atom)with a carbon number not less than 1 and not more than 6, and may be anyof straight-chain, branched and cyclic groups. In this case, examples ofthe hetero atom are an oxygen atom, a sulfur atom, a nitrogen atom, —OH,—OR²⁴, —O—, —S—, —S(═O)—, —NH₂, —NHR²⁴, —N(R²⁴)₂, —NH— and —NR²⁴—,wherein R²⁴ is an alkyl group.

Specific examples of R²² and R²³ used in Chemical Formula 22 are amethyl group, a hydroxymethyl group, an ethyl group, a hydroxyethylgroup, a propyl group, an isopropyl group, a n-butyl group, a sec-butylgroup, a n-pentyl group, a n-hexyl group, a methoxy group, amethoxymethoxy group, an ethoxy group and a tert-butoxy group.

Embodiment 3

A resist material according to Embodiment 3 of the invention will now bedescribed.

The resist material of Embodiment 3 includes, as a base polymer, thepolymer compound according to Embodiment 1 or 2.

It is noted that the resist material of Embodiment 3 may include anotherpolymer compound for the purpose of changing dynamical, thermal or otherproperties of a resultant resist film. In this case, the polymercompound to be additionally included is not particularly specified, butthe resist material preferably includes the polymer compound accordingto Embodiment 1 or 2 in a rate not less than 50% and not more than 70%of the whole base polymer.

Embodiment 4

A positive chemically amplified resist material according to Embodiment4 of the invention will now be described.

The chemically amplified resist material of Embodiment 4 includes thepolymer compound according to Embodiment 1 or 2 as a base polymer andalso includes an acid generator and an organic solvent. Furthermore, thechemically amplified resist material of Embodiment 4 includes a basiccompound serving as a buffer or an agent for improving dissolutioncontrast, or a dissolution inhibitor serving as an agent for improvingdissolution contrast.

Specific examples of the acid generator are diphenyliodoniumtrifluoromethanesulfonate, (p-tert-butoxyphenyl)phenyliodoniumtrifluoromethanesulfonate, diphenyliodonium p-toluenesulfonate,(p-tert-butoxyphenyl)phenyliodonium p-toluenesulfonate,triphenylsulfonium trifluoromethanesulfonate,(p-tert-butoxyphenyl)diphenylsulfonium trifluoromethanesulfonate, etc.In this case, one of these acid generators may be singly used or acombination of two or more of them may be used.

The content of the acid generator is preferably 0.2 through 15 parts byweight based on 100 parts by weight of the base polymer. When thecontent of the acid generator is smaller than 0.2 part by weight basedon 100 parts by weight of the base polymer, the amount of acid generatedin exposure is too small to attain high sensitivity and high resolution,and when it is larger than 15 parts by weight based on 100 parts byweight of the base polymer, the transparency may be so low that theresolution is lowered.

As the basic compound, a compound capable of suppressing a diffusingrate of an acid generated from the acid generator diffusing within aresultant resist film is suitably used. When the basic compound isincluded in the chemically amplified resist material, the diffusing rateof the acid within the resist film is suppressed and hence theresolution is improved. Therefore, exposure margin or pattern profilecan be improved by suppressing sensitivity change through the exposureor by reducing dependency on a substrate or environment.

Specific examples of the basic compound are ammonia, primary, secondaryor tertiary aliphatic amines, mixed amines, aromatic amines,heterocyclic amines, a nitrogen-containing compound having a carboxylgroup, a nitrogen-containing compound having a sulfonyl group, anitrogen-containing compound having a hydroxyl group, anitrogen-containing compound having a hydroxyphenyl group, an alcoholicnitrogen-containing compound, an amide derivative, an imide derivative,etc.

As the dissolution inhibitor, a compound with a molecular weight of3,000 or less and preferably of 2,500 or less whose solubility in analkaline developer is changed by a function of an acid is preferablyused, and specifically, a compound including phenol, a carboxylic acidderivative or hexafluoroisopropanol in which acid labile groups aresubstituted for part or whole of hydroxyl groups is suitably used.

The content of the dissolution inhibitor is preferably 20 parts byweight or less and more preferably 15 parts by weight or less based on100 parts by weight of the base polymer included in the resist material.When the content is larger than 20 parts by weight based on 100 parts byweight of the base polymer, the content of a monomer component is solarge that the heat resistance of the resist material is lowered.

The resist material of Embodiment 4 may include another polymer compoundfor the purpose of changing dynamical, thermal, alkali-soluble or otherproperties of a resultant resist film. In this case, the polymercompound to be additionally included is not particularly specified, andit may be mixed with the polymer compound according to Embodiment 1 or 2in an appropriate rate.

Embodiment 5

A pattern formation method according to Embodiment 5 of the inventionwill now be described.

In the pattern formation method of Embodiment 5, the resist materialaccording to Embodiment 3 or 4 is used, and the pattern formation methodincludes the following procedures:

First, the resist material according to Embodiment 3 or 4 is applied ona substrate such as a silicon wafer in a thickness of 0.1 through 1.0 μmby spin coating or the like. Thereafter, the resultant substrate issubjected to pre-bake by using a hot plate at a temperature of 60through 200° C. for 10 seconds through 10 minutes and preferably at atemperature of 80 through 150° C. for 30 seconds through 5 minutes.Thus, a resist film is formed.

Next, the resist film is irradiated through a photomask having a desiredpattern with high energy beams such as deep UV, excimer laser or X-rays,or electron beams at exposure of approximately 1 through 200 mJ/cm² andpreferably approximately 10 through 100 mJ/cm². Thereafter, theresultant is subjected to post-exposure bake (PEB) by using a hot plateat a temperature of 60 through 150° C. for 10 seconds through 5 minutesand preferably at a temperature of 80 through 130° C. for 30 secondsthrough 3 minutes.

Next, the resultant resist film is developed by using a developer of analkaline aqueous solution, such as tetramethylammonium hydroxide (TMAH),with a concentration of 0.1 through 5% and preferably 2 through 3% for10 seconds through 3 minutes and preferably 30 seconds through 2minutes. Thus, a resist pattern is formed. For this development, any ofknown methods such as a dip method, a puddle method and a spray methodcan be employed.

In Embodiment 5, the exposing light may be deep UV or excimer laser of awavelength of a 254 nm through 120 nm band, and in particular, highenergy beams such as KrF laser of a wavelength of a 248 nm band, ArFlaser of a wavelength of a 193 nm band, F₂ laser of a wavelength of a157 nm band, Kr₂ laser of a wavelength of a 146 nm band, KrAr laser of awavelength of a 134 nm band, Ar₂ laser of a wavelength of a 126 nm bandor soft X-rays, or electron beams. Thus, a fine resist pattern can beformed.

Now, specific experimental examples practiced for evaluating the patternformation method of Embodiment 5 will be described with reference toFIG. 2.

As is understood from FIG. 2, in the pattern formation method ofEmbodiment 5, the transmittance at a wavelength band of 157 nm islargely improved as compared with the case where poly(vinylphenol) ormethyl methacrylate is used as a base polymer.

EXAMPLE 1

Example 1 for embodying the chemically amplified resist material ofEmbodiment 4 and the pattern formation method of Embodiment 5 will nowbe described with reference to FIGS. 1A through 1D.

First, a chemically amplified resist material having the followingcomposition is prepared:

Base polymer: polymer in which a first unit represented by ChemicalFormula 23 and a second unit represented by Chemical Formula 24 arepolymerized

Acid generator: triphenylsulfonium triflate (2 wt % based on the basepolymer)

Solvent: propylene glycol monomethyl ether acetate

Next, as shown in FIG. 1A, the chemically amplified resist materialhaving the above-described composition is applied on a semiconductorsubstrate 10 by spin coating, thereby forming a resist film 11 with athickness of 0.2 μm. At this point, since the base polymer isalkali-insoluble, the resist film 11 is alkali-insoluble.

Next, as shown in FIG. 1B, the resist film 11 is subjected to patternexposure by irradiating through a mask 12 with exposing light 13 of ArFlaser (of a wavelength of a 193 nm band). Thus, an acid is generatedfrom the acid generator in an exposed portion 11 a of the resist film 11while no acid is generated in an unexposed portion 11 b of the resistfilm 11.

Then, as shown in FIG. 1C, the semiconductor substrate 10 together withthe resist film 11 is heated with a hot plate 14. Thus, the base polymeris heated in the presence of the acid in the exposed portion 11 a of theresist film 11, so as to release a protecting group in the second unit.As a result, the base polymer becomes alkali-soluble.

Subsequently, the resist film 11 is developed with an alkaline developersuch as a tetramethylammonium hydroxide aqueous solution. Thus, theexposed portion 11 a of the resist film 11 is dissolved in thedeveloper, so that a resist pattern 15 made of the unexposed portion 11b of the resist film 11 can be formed as shown in FIG. 1D.

In the pattern exposure shown in FIG. 1B, the resist film 11 may beselectively irradiated with the exposing light 13 with water or a liquid(having a refractive index n) such as perfluoropolyether supplied on theresist film 11. When such immersion lithography is performed, since aregion between a condensing lens and the resist film in an exposuresystem is filled with the liquid having a refractive index n, the valueof NA (numerical aperture) of the exposure system becomes a value n·NA,and hence the resolution of the resist film 11 is improved.

EXAMPLE 2

Example 2 for embodying the chemically amplified resist materialaccording to Embodiment 4 and the pattern formation method according toEmbodiment 5 will now be described. Since Example 2 is different fromExample 1 merely in the chemically amplified resist material and theexposing light 13, the resist material and the exposing light 13 alonewill be herein described.

First, a chemically amplified resist material having the followingcomposition is prepared:

Base polymer: polymer in which a first unit represented by ChemicalFormula 25 and a second unit represented by Chemical Formula 26 arepolymerized

Acid generator: triphenylsulfonium triflate (2 wt % based on the basepolymer)

Solvent: propylene glycol monomethyl ether acetate

Next, the chemically amplified resist material having the aforementionedcomposition is applied on a semiconductor substrate 10 by spin coating,so as to form a resist film 11 with a thickness of 0.2 μm. Thereafter,the resist film 11 is subjected to pattern exposure by irradiatingthrough a mask 12 with exposing light 13 of KrF laser (of a wavelengthof a 248 nm band).

EXAMPLE 3

Example 3 for embodying the chemically amplified resist materialaccording to Embodiment 4 and the pattern formation method according toEmbodiment 5 will now be described. Since Example 3 is different fromExample 2 merely in the chemically amplified resist material, the resistmaterial alone will be herein described.

A chemically amplified resist material having the following compositionis prepared:

Base polymer: polymer in which a first unit represented by ChemicalFormula 27 and a second unit represented by Chemical Formula 28 arepolymerized

Acid generator: triphenylsulfonium triflate (2 wt % based on the basepolymer)

Solvent: propylene glycol monomethyl ether acetate

EXAMPLE 4

Example 4 for embodying the chemically amplified resist materialaccording to Embodiment 4 and the pattern formation method according toEmbodiment 5 will now be described. Since Example 4 is different fromExample 2 merely in the chemically amplified resist material, the resistmaterial alone will be herein described.

A chemically amplified resist material having the following compositionis prepared:

Base Polymer:

-   -   poly(acrylsulfonamide₆₀-acrylsulfone-N-adamantyloxydiethylamide₄₀)

Acid generator: triphenylsulfonium triflate (3 wt % based on the basepolymer)

Solvent: propylene glycol monomethyl ether acetate

EXAMPLE 5

Example 5 for embodying the chemically amplified resist materialaccording to Embodiment 4 and the pattern formation method according toEmbodiment 5 will now be described. Since Example 5 is different fromExample 2 merely in the chemically amplified resist material, the resistmaterial alone will be herein described.

A chemically amplified resist material having the following compositionis prepared:

Base polymer: poly(acrylsulfone-N-adamantyloxyethylamide)

Acid generator: triphenylsulfonium triflate (3 wt % based on the basepolymer)

Solvent: propylene glycol monomethyl ether acetate

Embodiment 6

A pattern formation method according to Embodiment 6 of the inventionwill now be described.

In the pattern formation method of Embodiment 6, immersion lithographyfor performing exposure with water provided between a resist film and anexposure lens is carried out by using the resist material according toEmbodiment 3 or 4. This pattern formation method includes the followingprocedures:

First, the resist material according to Embodiment 3 or 4 is applied ona substrate such as a silicon wafer in a thickness of 0.1 through 1.0 μmby spin coating or the like. Thereafter, the resultant substrate issubjected to pre-bake by using a hot plate at a temperature of 60through 200° C. for 10 seconds through 10 minutes and preferably at atemperature of 80 through 150° C. for 30 seconds through 5 minutes.Thus, a resist film is formed.

Next, with a liquid supplied on the resist film, the resist film isirradiated through a photomask having a desired pattern with high energybeams such as deep UV, excimer laser or X-rays, or electron beams atexposure of approximately 1 through 200 mJ/cm² and preferablyapproximately 10 through 100 mJ/cm².

Thereafter, the resultant is subjected to post-exposure bake (PEB) byusing a hot plate at a temperature of 60 through 150° C. for 10 secondsthrough 5 minutes and preferably at a temperature of 80 through 130° C.for 30 seconds through 3 minutes.

Next, the resultant resist film is developed by using a developer of analkaline aqueous solution, such as tetramethylammonium hydroxide (TMAH),with a concentration of 0.1 through 5% and preferably 2 through 3% for10 seconds through 3 minutes and preferably 30 seconds through 2minutes. Thus, a resist pattern is formed. For this development, any ofknown methods such as a dip method, a puddle method and a spray methodcan be employed.

In Embodiment 6, the exposing light may be deep UV or excimer laser of awavelength of a 254 nm through 120 nm band, and in particular, highenergy beams such as KrF laser of a wavelength of a 248 nm band, ArFlaser of a wavelength of a 193 nm band, F₂ laser of a wavelength of a157 nm band, Kr₂ laser of a wavelength of a 146 nm band, KrAr laser of awavelength of a 134 nm band, Ar₂ laser of a wavelength of a 126 nm bandor soft X-rays, or electron beams. Thus, a fine resist pattern can beformed.

Apart from water, a liquid (having a refractive index n) such asperfluoropolyether may be supplied on the resist film 11 in the patternexposure for selectively irradiating the resist film with the exposinglight. When such immersion lithography is performed, since a regionbetween a condensing lens and the resist film in an exposure system isfilled with the liquid having a refractive index n, the value of NA(numerical aperture) of the exposure system becomes a value n·NA, andhence, the resolution of the resist film is improved.

EXAMPLE 6

Example 6 for embodying the chemical amplified resist material accordingto Embodiment 4 and the pattern formation method according to Embodiment6 will now be described with reference to FIGS. 3A through 3D.

First, a chemically amplified resist material having the followingcomposition is prepared:

Base polymer: polymer in which a first unit represented by ChemicalFormula 29 and a second unit represented by Chemical Formula 30 arepolymerized

Acid generator: triphenylsulfonium triflate (2 wt % based on the basepolymer)

Solvent: propylene glycol monomethyl ether acetate

Next, as shown in FIG. 3A, the chemically amplified resist materialhaving the above-described composition is applied on a semiconductorsubstrate 101 by spin coating, thereby forming a resist film 102 with athickness of 0.2 μm. At this point, since the base polymer isalkali-insoluble, the resist film 102 is alkali-insoluble.

Next, as shown in FIG. 3B, the resist film 102 is subjected to patternexposure by irradiating through an exposure lens 104 with exposing lightof ArF laser (of a wavelength of a 193 nm band) with water 103 (having arefractive index n of 1.44) provided on the resist film 102. Thus, anacid is generated from the acid generator in an exposed portion 102 a ofthe resist film 102 while no acid is generated in an unexposed portion102 b of the resist film 102.

Then, as shown in FIG. 3C, the semiconductor substrate 101 together withthe resist film 102 is heated with a hot plate. Thus, the base polymeris heated in the presence of the acid in the exposed portion 102 a ofthe resist film 102, so as to release a protecting group in the secondunit. As a result, the base polymer becomes alkali-soluble.

Subsequently, the resist film 102 is developed with an alkalinedeveloper such as a tetramethylammonium hydroxide aqueous solution.Thus, the exposed portion 102 a of the resist film 102 is dissolved inthe developer, so that a resist pattern 105 made of the unexposedportion 102 b of the resist film 102 can be formed as shown in FIG. 3D.

It is noted that the base polymer includes the unit represented byChemical Formula 29 in a rate of approximately 45% and the unitrepresented by Chemical Formula 30 in a rate of approximately 55%.

In the case where the base polymer includes a plurality of kinds ofunits in this manner, the respective units are preferably polymerized ina comparatively homogeneous state. When the different units are wellmixed in the base polymer by preventing a given unit from polymerizinglocally in a given portion of the base polymer, the respective units canbe polymerized in such a manner as to be engaged with one another. Thus,the skeleton strength of the resultant base polymer can be improved.Therefore, the effect to improve the transparency and the hydrophilicproperty owing to the sulfonamide group can be attained and a basepolymer including at least two kinds of units and having highpolymerization uniformity can be provided. As a result, a resist patternwith improved etching resistance can be formed in a good shape.

In addition, when the polymerization uniformity of the units used forforming a resist film is improved, particularly in employing theexposure by the immersion lithography, permeation of an immersion liquidinto the resist film and elution of components of the resist film intothe immersion liquid can be suppressed. This is because, when thepolymerization uniformity is high, different kinds of units are engagedwith one another so as to be sterically bonded to one another in aresultant polymer structure, and hence, the structure of the resultantresist film is complicated. Accordingly, even in the exposure by theimmersion lithography in which the immersion liquid and the resist filmare in direct contact with each other, mutual dissolution of theircomponents can be prevented. As a result, a pattern can be accuratelyformed.

The resist material or the pattern formation method of this invention isparticularly suitable to a method for forming a fine resist pattern in ashape vertical to a substrate by using exposing light of KrF laser, ArFlaser, F₂ laser, KrAr laser or Ar₂ laser.

1. A polymer compound comprising a unit represented by a general formulaof the following Chemical Formula 2 and having a weight-averagemolecular weight of 1,000 or more and 500,000 or less:

wherein R¹, R² and R³ are the same or different and are a hydrogen atom,a fluorine atom, a straight-chain alkyl group, a branched or cyclicalkyl group or a fluoridated alkyl group with a carbon number not lessthan 1 and not more than 20; R⁴ is a straight-chain alkylene group or abranched or cyclic alkylene group with a carbon number not less than 0and not more than 20; and at least one of R⁵ and R⁶ is a protectinggroup released by an acid.
 2. A resist material comprising a basepolymer containing a polymer compound including a unit represented by ageneral formula of the following Chemical Formula 3:

wherein R¹, R² and R³ are the same or different and are a hydrogen atom,a fluorine atom, a straight-chain alkyl group, a branched or cyclicalkyl group or a fluoridated alkyl group with a carbon number not lessthan 1 and not more than 20; R⁴ is a straight-chain alkylene group or abranched or cyclic alkylene group with a carbon number not less than 0and not more than 20; and at least one of R⁵ and R⁶ is a protectinggroup released by an acid.
 3. The resist material of claim 2, whereinsaid protecting group released by an acid is an acetal group.
 4. Theresist material of claim 3, wherein said acetal group is an alkoxyethylgroup or an alkoxymethyl group.
 5. The resist material of claim 4,wherein said alkoxyethyl group is an adamantyloxyethyl group, at-butyloxyethyl group, an ethoxyethyl group or a methoxyethyl group, andsaid alkoxymethyl group is an adamantyloxymethyl group, at-butyloxymethyl group, an ethoxymethyl group or a methoxymethyl group.6. The resist material of claim 2, further comprising an acid generatorfor generating an acid through irradiation with light.
 7. The resistmaterial of claim 6, further comprising a dissolution inhibitor forinhibiting dissolution of said base polymer.